Widely-accepted Model Research Articles

1440Anti-inflammatory adipokine, omentin, attenuates angiotensin II-induced abdominal aortic aneurysm formation in apolipoprotein-E knockout mice

Abstract Background Abdominal aortic aneurysm (AAA) is an increasing and life-threatening disease. Obesity is associated with an increased risk of AAA. Omentin is a circulating adipokine, which is downregulated by obesity. Recently we have demonstrated that omentin is an anti-inflammatory adipokine that prevents the development of atherosclerosis in apolipoprotein-E knockout (apoE-KO) mice. Here we examined whether omentin could modulate angiotensin II-induced AAA formation in apoE-KO mice. Methods and results To overexpress human omentin in apoE-KO mice, apoE-KO mice were crossed with transgenic mice expressing the human omentin gene in fat tissue under the control of AP2 promoter (OMT-Tg mice). Circulating levels of human omentin in apoE-KO/OMT-Tg mice were approximately threefold higher than those in healthy human subjects, whereas human omentin was undetectable in apoE-KO mice. There were no differences in body weight, blood pressure and heart rate between apoE-KO/OMT-Tg and apoE-KO mice. We also subjected apoE-KO/OMT-Tg and apoE-KO mice at 24 weeks of age to continuous angiotensin II-infusion by using osmotic mini pumps for 4 weeks, which is a widely-accepted model of experimental AAA. ApoE-KO/OMT-Tg mice exhibited a lower incidence of AAA formation and a reduced maximal diameter of AAA determined by direct measurement and ultrasound imaging as compared with apo-E KO mice. In histological analyses with van Gieson staining, apoE-KO/OMT-Tg mice showed attenuated disruption of medial elastic fibers in response to angiotensin II compared with apo-E KO mice. ApoE-KO/OMT-Tg mice also displayed reduced mRNA levels of matrix metalloproteinase (MMP) 2 and MMP9 as well as pro-inflammation genes including interleukin (IL)-6 in aortic walls compared with apo-E KO mice. Treatment of human monocyte-derived macrophages with human omentin protein attenuated LPS-stimulated expression of MMP9, TNF-α and IL-6. Omentin treatment also reduced LPS-induced activation of MMP9 in cultured media of human macrophages as evaluated by gelatinolytic zymography. Omentin treatment increased phosphorylation levels of Akt in human macrophages. The suppressive effects of omentin on inflammatory response in macrophages were reversed by treatment with LY294002, which is an inhibitor of PI3 kinase/Akt signaling. Conclusion These data suggest that omentin acts as an adipokine that can attenuate angiotensin II-induced development of AAA through suppression of MMP activation and inflammatory response in the vascular wall.

Independent production of distinct monocyte subsets by granulocyte-monocyte progenitors (GMPS) and monocyte-dendritic cell progenitors (MDPS)

Myelopoiesis, the production of myeloid cells by hematopoietic stem and progenitor cells, must be carefully regulated to support immune surveillance in the steady-state and meet the additional demands of emergency conditions such as infection. The current widely-accepted model of myelopoiesis describes the production of neutrophils by granulocyte-monocyte progenitors (GMPs), which also yield monocytes and dendritic cells (DCs) via monocyte-DC progenitors (MDPs). However, our studies have revealed that murine GMPs do not give rise to MDPs, and that conventional and plasmacytoid DCs (cDCs and pDCs) are produced by MDPs but not GMPs. Instead, we have discovered that GMPs and MDPs arise separately, and that both yield Ly6Chi monocytes and Ly6C- CD43+ monocytes. However, GMP- and MDP-derived Ly6Chi monocytes are morphologically distinct and exhibit differences in gene expression that are defined by their origins. GMPs produce a subset of Ly6Chi monocytes that are larger and more granular than MDP-derived Ly6Chi monocytes, and enriched for granule proteins including myeloperoxidase. In contrast, monocyte-derived DCs arise from the MDP pathway and are not produced by GMPs. We also show that the GMP and MDP pathways are mobilized independently in response to microbial stimuli. Lipopolysaccharide administration increases neutrophil and monocyte production by GMPs, while CpG DNA promotes monocyte and cDC production by MDPs. Thus, the existence of two independent pathways of monocyte differentiation permits the production of specific combinations of myeloid cell types during the emergency myelopoiesis response to pathogens via differential targeting of GMPs and MDPs.

Using eCoaching to Improve Practice of Novice Teacher Educators

Coaching is becoming a more widely-accepted model of support for both preservice and inservice P-12 teachers. With the use of technology such as Bluetooth headsets and live streaming, coaching has become less intrusive and more “in the moment.” In this case study, we describe the use of an eCoaching process for two PhD students who taught courses in a teacher preparation program of a higher education institution. The four-step process included (a) observing the PhD students teach, (b) collaboratively developing instructional goals with the coach, (c) providing performance feedback while coaching, and (d) reflecting on the process with the two PhD students who were teaching undergraduate courses. Findings indicate that eCoaching was well received and provided multiple opportunities for both PhD students and their coach to reflect on instruction as well as the eCoaching process. Implications for practice and future research are discussed.

Monte-Carlo simulation of defect-cluster nucleation in metals during irradiation

A multiscale modeling approach was applied to investigate the nucleation process of CRPs (copper rich precipitates, i.e., copper-vacancy clusters) in α-Fe containing 1at.% Cu during irradiation. Monte-Carlo simulations were performed to investigate the nucleation process, with the rate theory equation analysis to evaluate the concentration of displacement defects, along with the molecular dynamics technique to know CRP thermal stabilities in advance. Our MC simulations showed that there is long incubation period at first, followed by a rapid growth of CRPs. The incubation period depends on irradiation conditions such as the damage rate and temperature. CRP’s composition during nucleation varies with time. The copper content of CRPs shows relatively rich at first, and then becomes poorer as the precipitate size increases. A widely-accepted model of CRP nucleation process is finally proposed.

Characterization of human translesion DNA synthesis across a UV-induced DNA lesion.

Translesion DNA synthesis (TLS) during S-phase uses specialized TLS DNA polymerases to replicate a DNA lesion, allowing stringent DNA synthesis to resume beyond the offending damage. Human TLS involves the conjugation of ubiquitin to PCNA clamps encircling damaged DNA and the role of this post-translational modification is under scrutiny. A widely-accepted model purports that ubiquitinated PCNA recruits TLS polymerases such as pol η to sites of DNA damage where they may also displace a blocked replicative polymerase. We provide extensive quantitative evidence that the binding of pol η to PCNA and the ensuing TLS are both independent of PCNA ubiquitination. Rather, the unique properties of pols η and δ are attuned to promote an efficient and passive exchange of polymerases during TLS on the lagging strand.

Independent production of distinct monocyte subsets by granulocyte-monocyte progenitors (GMPs) and monocyte-dendritic cell progenitors (MDPs)

Abstract Myeloid cells – neutrophils, monocytes and dendritic cells (DCs) – play key roles in inflammation, immune defense against pathogens, and tissue repair and remodeling. Myelopoiesis, the production of myeloid cells by hematopoietic stem and progenitor cells, must be carefully regulated to support immune surveillance in the steady-state and meet the additional demands of emergency conditions such as infections. The current widely-accepted model of myelopoiesis describes the production of neutrophils by granulocyte-monocyte progenitors (GMPs), which also yield monocytes and DCs via monocyte-DC progenitors (MDPs). However, our data show that murine GMPs do not give rise to MDPs and that conventional and plasmacytoid DCs (cDCs and pDCs) are produced by MDPs but not GMPs. Thus GMPs and MDPs arise separately but both yield monocytes. Our in vitro and in vivo studies of the pathways and mechanisms of monocyte production have revealed that both GMPs and MDPs yield Ly6C+ inflammatory monocytes and Ly6C− CD43+ monocytes, but that GMP-derived and MDP-derived Ly6C+ inflammatory monocytes exhibit distinct patterns of gene expression. In ongoing studies we are comparing the phenotype and function of GMP- and MDP-derived monocytes, and determining the relative contributions of GMPs and MDPs to the monocyte and tissue macrophage pools under steady-state and emergency conditions.

Book review: Advances in the understanding of gluten related pathology and the evolution of gluten-free foods; Edited by: Eduardo Arranz, Fernando Fernández Bañares, Cristina M. Rosell, Luis Rodrigo, Amado Salvador Peña

Book review: Advances in the understanding of gluten related pathology and the evolution of gluten-free foods; Edited by: Eduardo Arranz, Fernando Fernández Bañares, Cristina M. Rosell, Luis Rodrigo, Amado Salvador Peña

Two-Round Password-Only Authenticated Key Exchange in the Three-Party Setting

We present the first provably-secure three-party password-only authenticated key exchange (PAKE) protocol that can run in only two communication rounds. Our protocol is generic in the sense that it can be constructed from any two-party PAKE protocol. The protocol is proven secure in a variant of the widely-accepted model of Bellare, Pointcheval and Rogaway (2000) without any idealized assumptions on the cryptographic primitives used. We also investigate the security of the two-round, three-party PAKE protocol of Wang, Hu and Li (2010) and demonstrate that this protocol cannot achieve implicit key authentication in the presence of an active adversary.

A provably-secure ECC-based authentication scheme for wireless sensor networks.

A smart-card-based user authentication scheme for wireless sensor networks (in short, a SUA-WSN scheme) is designed to restrict access to the sensor data only to users who are in possession of both a smart card and the corresponding password. While a significant number of SUA-WSN schemes have been suggested in recent years, their intended security properties lack formal definitions and proofs in a widely-accepted model. One consequence is that SUA-WSN schemes insecure against various attacks have proliferated. In this paper, we devise a security model for the analysis of SUA-WSN schemes by extending the widely-accepted model of Bellare, Pointcheval and Rogaway (2000). Our model provides formal definitions of authenticated key exchange and user anonymity while capturing side-channel attacks, as well as other common attacks. We also propose a new SUA-WSN scheme based on elliptic curve cryptography (ECC), and prove its security properties in our extended model. To the best of our knowledge, our proposed scheme is the first SUA-WSN scheme that provably achieves both authenticated key exchange and user anonymity. Our scheme is also computationally competitive with other ECC-based (non-provably secure) schemes.

수리거동곡선 모형의 개발 및 적용

This paper presents a hydraulic performance graph model in which the flow carrying capacity of a channel system was determined by accounting the interacting backwater effect among channel reaches and incoming lateral flow. The method utilizes hydraulic performance graphs(HPGs), and the method is applied to a natural channel Nakdong River to examine its applicability. This research shows that estimation results using HPG are close to records from the stage station and the results from a widely-accepted model, HEC-RAS. Assuming that a water level gage site is ungaged, water level estimations by HPGs compared with observation show that with a flood event, the HPGs underestimate in the water level ascension phase, but in the recession phase they overestimate results. The accuracy of estimation with HPGs was greatly improved by considering the time difference of flooding between the observation and estimation locations.

Average structure and local configuration of excess oxygen in UO2+x

Determination of the local configuration of interacting defects in a crystalline, periodic solid is problematic because defects typically do not have a long-range periodicity. Uranium dioxide, the primary fuel for fission reactors, exists in hyperstoichiometric form, UO2+x. Those excess oxygen atoms occur as interstitial defects, and these defects are not random but rather partially ordered. The widely-accepted model to date, the Willis cluster based on neutron diffraction, cannot be reconciled with the first-principles molecular dynamics simulations present here. We demonstrate that the Willis cluster is a fair representation of the numerical ratio of different interstitial O atoms; however, the model does not represent the actual local configuration. The simulations show that the average structure of UO2+x involves a combination of defect structures including split di-interstitial, di-interstitial, mono-interstitial, and the Willis cluster, and the latter is a transition state that provides for the fast diffusion of the defect cluster. The results provide new insights in differentiating the average structure from the local configuration of defects in a solid and the transport properties of UO2+x.

Beyond Internet Universalism: A Framework for Addressing Cross-Border Internet Policy

The Internet is a global network that is fundamental to commerce, communication, and culture. The ability to use the Internet to purchase products and services from halfway around the world, to talk to friends and strangers in other countries, and to share and discover new ideas, is what has made the Internet the defining technology of the 21st century. But the same capabilities that make the Internet the incredible powerhouse that contributes trillions of dollars annually to the global economy — the ability to transfer data seamlessly across geographic borders — has exacerbated the international conflicts that arise between nations with different laws and values. Even though the importance of the Internet to the global economy and society continues to grow each day, collectively nations have made little substantive progress in creating a framework for resolving the many conflicts over Internet policy that inevitably occur between sovereign nations. These conflicts arise over a myriad of issues, such as free speech, intellectual property, privacy, cybercrime, consumer protection, taxation, commerce regulation, and others. To date, despite many attempts, no framework has been successful at providing a practical and widely-accepted model for policymakers to resolve cross-border Internet policy conflicts in ways that respect both the global nature of the Internet and national laws and norms. One reason for the lack of progress is that different nations have different sets of values and priorities, and attempts at resolving policy disputes inevitably falter because the various parties lack a common basis for dialogue. Another reason is that many proposed frameworks tend to apply a particular nation’s worldview on the rest of the world, such as promoting democracy and freedom of expression (as in the case of the United States) or maintaining political control (as in the case of nations like China and Russia). But despite their appeal (e.g., they would be relatively easy to administer if everyone would just agree to one universal framework), such frameworks simply cannot work because nations have significantly different cultural values, policy priorities, and legal systems. It is highly unlikely Europe will agree to a U.S. privacy framework (or that the United States will agree to an EU privacy framework), or that Saudi Arabia will agree to U.S. free speech framework, especially when it comes to Internet pornography. But the alternative, a Balkanized, fragmented global Internet that gives nations the right to act on the Internet with impunity cannot be the answer either. What is needed is a framework that allows nations the right to customize Internet policy to their own national needs and rules, while at the same time constraining those rights in ways that enable global Internet commerce and digital free trade while also preserving the underlying global Internet architecture, like the global domain name system. While nations will not always agree unanimously on specific policy proposals, appropriate solutions, or even the relevant evidence, a common framework of understanding cross-border Internet policy issues will allow for healthier Internet policy debates, better cooperation and coordination between nations, and fewer policy conflicts. This report explores the nature of cross-border Internet policy conflicts and provides a sample of the types of conflicts that have been seen in recent years. It also discusses the limitations of existing Internet policy frameworks, offers an alternative perspective and outlines a specific set of rules that should be used for evaluating cross-border Internet policy conflicts. Finally, it operationalizes this framework using various examples to show the method in action.

SREBP‐2: A link between insulin resistance, hepatic cholesterol, and inflammation in NASH

See article in J. Gastroenterol. Hepatol. 2011; 26: 875–883.

Accurate LAI retrieval method based on PROBA/CHRIS data

Abstract. Leaf area index (LAI) is one of the key structural variables in terrestrial vegetation ecosystems. Remote sensing offers an opportunity to accurately derive LAI at regional scales. The anisotropy of canopy reflectance, variations in background characteristics, and variability in atmospheric conditions constitute three factors that can strongly constrain the accuracy of retrieved LAI. Based on a hybrid canopy reflectance model, a new hyperspectral directional second derivative method (DSD) is proposed in this paper. This method can estimate LAI accurately through analyzing the canopy anisotropy. The effect of the background can also be effectively removed. With the aid of a widely-accepted atmospheric model, the influence of atmospheric conditions can be minimized as well. Thus the inversion precision and the dynamic range can be markedly improved, which has been proved by numerical simulations. As the derivative method is very sensitive to random noise, we put forward an innovative filtering approach, by which the data can be de-noised in spectral and spatial dimensions synchronously. It shows that the filtering method can remove random noise effectively; therefore, the method can be applied to hyperspectral images. The study region was situated in Zhangye, Gansu Province, China; hyperspectral and multi-angular images of the study region were acquired via the Compact High-Resolution Imaging Spectrometer/Project for On-Board Autonomy (CHRIS/PROBA), on 4 June 2008. After the pre-processing procedures, the DSD method was applied, and the retrieved LAI was validated by ground reference data at 11 sites. Results show that the new LAI inversion method is accurate and effective with the aid of the innovative filtering method.

Could stroma contribute to field cancerization?

The common oral diseases as well as oral cancer have the characteristic of field cancerization or field effect. Field cancerization, characterized by phenotypic and genetic changes in the neighboring cells of the frank cancer cells, is a clinical phenomenon first found in head and neck cancers. Field cancerization of the epithelia is currently a widely-accepted model in cancer biology as a manifestation of cancer progression. The concomitant changes in the tumor microenvironment have drawn more attention recently. Could the changes in the tumor microenvironment and the epithelial field cancerization concepts be linked? In view of the importance of stroma in the development of epithelium and evidence in carcinoma-associated stroma, we propose the question if stroma not only reciprocates the neoplastic changes of the epithelia, but also contributes to field cancerization. Actually one perspective paper pointed out that healing wound can influence the recurrence of field cancerization. In another words, the microenvironment of healing wound determines the prognosis of field cancerization. Based on the literatures published and our own work, we hypothesize a new model of field cancerization focusing on the co-evolution of the tumor microenvironment. We suggest that the microenvironment cannot be neglected when treating diseases with characteristics of field cancerization.

Resolving cadherin interactions and binding cooperativity at the single-molecule level

The cadherin family of Ca(2+)-dependent cell adhesion proteins are critical for the morphogenesis and functional organization of tissues in multicellular organisms, but the molecular interactions between cadherins that are at the core of cell-cell adhesion are a matter of considerable debate. A widely-accepted model is that cadherins adhere in 3 stages. First, the functional unit of cadherin adhesion is a cis dimer formed by the binding of the extracellular regions of 2 cadherins on the same cell surface. Second, formation of low-affinity trans interactions between cadherin cis dimers on opposing cell surfaces initiates cell-cell adhesion. Third, lateral clustering of cadherins cooperatively strengthens intercellular adhesion. Evidence of these cadherin binding states during adhesion is, however, contradictory, and evidence for cooperativity is lacking. We used single-molecule structural (fluorescence resonance energy transfer) and functional (atomic force microscopy) assays to demonstrate directly that cadherin monomers interact via their N-terminal EC1 domain to form trans adhesive complexes. We could not detect the formation of cadherin cis dimers, but found that increasing the density of cadherin monomers cooperatively increased the probability of trans adhesive binding.

The Brand Management Efforts of a Niche Specialist: New Balance in the Athletic Footwear Industry

Introduction One per cent per year--the overall US market share growth goal recently stated by New Balance CEO Jim Davis (Steven David, Product Marketing Manager, New Balance, personal interview, August 18, 1998). Such a goal would be quite modest for one of its larger publicly owned competitors. But for New Balance Athletic Shoe, Inc, a privately-owned manufacturer in the highly-competitive athletic footwear industry, this represents a significant management challenge. No longer can the company be content to serve its loyal base of baby boomers (40- to 55-year-olds), it now must court Generation X (25- to 35-year-olds). This study illustrates the management efforts of a niche specialist, New Balance Athletic Shoe, Inc. Based in Boston, Massachusetts, USA, New Balance is a privately-held corporation whose 1998 estimated revenues of $550 million amounted to less than industry leader Nike spent on advertising in that year. While particular interest is paid to the branding efforts of New Balance, its efforts are analyzed in comparison to those of the three market leaders, publicly-owned corporations Nike, Reebok, and Adidas. This case study is comprised of five sections. The first section provides a brief overview of theory. The second section highlights the current status and trends of the athletic footwear industry in the United States. Using theory, the third section presents a summary of the management practices of Nike, Reebok, and Adidas. Based on this analysis, the fourth section provides a detailed account of how New Balance manages its to differentiate itself from its competitors. The case study concludes by offering conclusions about the management efforts of a niche specialist in a fiercely competitive industry. While derived from the athletic footwear industry, these conclusions are also salient for the broader sporting goods industry. An Overview of Brand Management The effort to create and manage brands is a practice widely studied by marketers throughout the world. Keller (1998) defines a as a name or symbol attached to a product that allows for differentiation from similar product offerings. For example, both the Nike name and the ubiquitous swoosh logo are components of the overall Nike brand. The goal of management is to continually build on the strength associated with a brand, thus developing strength, or equity. The set of assets (both positive and negative) that consumers attach to a particular constitute brand (Aaker, 1991). Many researchers have undertaken efforts to dissect equity into different components and dimensions. Perhaps the most widely-accepted model for understanding equity was presented by Aaker (1991), who suggested equity is comprised of five components: 1) Brand awareness 2) Perceived quality 3) Brand loyalty 4) Brand associations 5) Other proprietary assets The remainder of this section will focus on describing these five components as a basis for analysis of management practices in the athletic footwear industry. Brand Awareness Brand awareness is the starting point in the development of equity. It represents the consumer's ability to recall a name when given a product category (Aaker, 1991). For example, when a person is asked to name a of basketball shoes, they are more likely to mention Nike, Reebok, Converse or Adidas than they are to name LA Gear or Spalding. According to Keller (1998), awareness is important to strategy for three reasons. First, awareness of the ensures the enters the consumer's consideration set when looking to make a purchase. Second, awareness can affect choices within the consideration set. If one has a larger presence through advertising, it may be considered more favorably. …

TOWARD A LEXICAL PROCESSING MODEL FOR THE STUDY OF SECOND LANGUAGE VOCABULARY ACQUISITION

A major requirement for theory development in L2 vocabulary acquisition is an adequate model of L2 lexical organization and processing. At present, there is no widely accepted model of this kind, but recent research has demonstrated the potential usefulness of Levelt's (1989, 1993) L1 speech processing model (de Bot & Schreuder, 1993; Green, 1993; Poulisse, 1993). This paper explores the relevance of the model as adapted for L2 lexical processing of written texts, with particular attention to its mental lexicon components (concepts, lemmas, and lexemes) and organization. The model is first discussed in terms of its relevance to L2 lexical access, retrieval, and acquisition processes. Findings of an introspective L2 vocabulary study follow, detailing how university ESL learners reported dealing with unfamiliar words while carrying out L2 reading tasks. The information provided on their lexical inferencing strategy and varied knowledge sources used in the process provide support for the lexical components and organization proposed by Levelt. It is argued in this paper that the process of inferring the features of unknown words in a reading passage can be described in terms of lemma construction, as defined in the model.

PHYSICAL CONDITIONS OF MOLECULAR GAS IN THE GALAXY

ABSTRACT Physical conditions of molecular clouds in the Milky Way are examined through extensive observations of CO (J = 2-1) emission with the University of Tokyo-NRO 60 cm radio telescope. We take two complementary approaches-- large-scale mapping observations of nearby molecular clouds and an out-of-plane survey of the Milky Way. The observed CO (J = 2-1) intensity is compared with the CO (J = 1-0) data taken with the same angular resolution. Through a numerical calculation based on a large velocity gradient approximation, the CO (J = 2-1)/CO (J = 1-0) intensity ratio (equiv R2-1/1-0) is found to be a useful tool for researches of large-scale structure of molecular clouds. Molecular gas is classified in terms of the R}2-1/1-0 value; Very High Ratio Gas (VHRG; R2-1/1-0 >>1), High Ratio Gas (HRG; R_{2-1/1-0 ~0.8), Low Ratio Gas (LRG; R2-1/1-0 ~0.5) and Very Low Ratio Gas (VLRG; R2-1/1-0 <0.4). The VHRG is optically thin, dense and warm gas. The HRG is opaque and dense enough for low-J transitions of CO to be excited to the local thermodynamical equilibrium through collisions, while the LRG is less dense and the excitation of these low-J transitions is inefficient. For the HRG and the LRG, the R2-1/1-0 value is sensitive to the variation of gas density rather than gas kinetic temperature. The VLRG is faint and usually not detected in quick surveys. The apparent discrepancy of the observed line intensity and that predicted by the ratio of these intensities can be used to estimate the degree of beam dilution. Giant molecular clouds show large-scale systematic variation of gas density according to the location in the molecular clouds. Contrary to the widely-accepted model of molecular clouds, peripheral regions of GMCs are faint not because surface filling factor of line-emitting gas clumps is small but because even the low-J transitions of 12 CO are not excited enough due to low gas density in clumps in these regions. Heating and compression by associated young stars are efficient within several parsecs from the stars, and they do not enhance the R2-1/1-0 value in a cloud-scale because of this small range of influence. A systematic variation of the R2-1/1-0 value across the Galactic plane was observed. The ratio varies from ~0.75 at 4 kpc to ~0.6 at 8 kpc in galactocentric distance. The corresponding nT values derived by the one-zone model analysis are 8 X 103 and 4 X 103 cm-3 K, respectively. This trend can be understood by large-scale variation of mixing ratio of HRG and LRG as a function of galactocentric distance. On the other hand, there is little, if any, evidence for the difference of physical conditions between the in-plane gas and the out-of-plane gas. There is concentration of HRG along 'the Sagittarius arm' and 'the Scutum arm' found in l- V diagrams. This supports an idea that strong arms exist in the inner Galaxy and they compress molecular gas to contain much of HRG. Analysis of tangential components indicates that the scale height of molecular gas in interarm regions is larger by the factor of 1.5 than in arm regions. Molecular gas with higher R2-1/1-0 value are concentrated to the central ridge-like condensation of massive cloud, the inner Galaxy and the arms, rather than to the cloud envelopes, the outer Galaxy and the interarm regions, respectively. These tendency indicate that virtually all of the regions with high R2-1/1-0 ratio have one feature in common-- they concentrate to the regions with higher gas pressure. This fact as well as the central deficiency of atomic gas compared to molecular gas indicate that the large-scale properties of molecular gas are dominated by the compression processes such as shock compression by density-waves and gravitational collapse, and not by dissociative stripping of low-density gas due to UV photons. Since the Milky Way is the only galaxy in which we can learn about the effects of heating and compression in various scales on physical conditions of molecular gas, the above knowledge about the dominant mechanism for the compression of molecular gas will be used as a guideline for extragalactic works.

The role of compound formation and heteroepitaxy in indium-based ohmic contacts to GaAs

Ohmic contacts to n-GaAs formed by the heat treatment of In films have been investigated. The widely-accepted model for ohmic contact formation, involving the establishment of a heavily-doped layer, fails in this case because In is not a n-type dopant in GaAs. It is shown that the heat treatment results in the formation of a graded InxGa1−xAs (0≤x&amp;lt;1) heterojunction. This heterojunction is responsible for the ohmic behavior.